The present invention relates to a system for embedding data in an audio signal and to its subsequent recovery, which can be used for watermarking, data communications, audience surveying etc. The invention has particular relevance, to a system for hiding data in an audio signal by adding echoes to the audio signal and to a system for recovering the hidden data by detecting the added echoes.
U.S. Pat. No. 5,893,067 discloses a technique for hiding data within an audio signal for transmission to a remote receiver. The data is hidden in the audio signal by adding an artificial echo to the audio signal and varying the amplitude and/or delay of the echo in accordance with the data to be hidden.
A problem with the data hiding technique described in U.S. Pat. No. 5,893,067 is that in most situations, natural echoes can mask the artificial echoes making it difficult for the receiver to be able to identify the artificial echoes and hence recover the hidden data.